Genovese crime boss Vincent “Chin” Gigante, who used a “crazy act” to dodge the feds for years, tried to bribe a U.S. marshal with $1 million to help overturn his 1997 racketeering rap, an FBI report charges.

Gigante, dubbed the “Oddfather” for antics like showering with an umbrella and wandering his Greenwich Village neighborhood in a bathrobe, was convicted in July 1997 on racketeering and murder-conspiracy charges and is serving a 12-year prison term.

A secret Sept. 8, 1998, FBI report obtained by The Post charges that Gigante hatched a plot to get to a U.S. marshal who guarded the jurors and bribe him to come forward with phony testimony of jury misconduct.

The anonymous jury that convicted Gigante was escorted to and from the Brooklyn federal courthouse by marshals to prevent any possible tampering.

Gigante, 73, was heavily sedated during the trial and transported to and from court in a wheelchair.

In the FBI report, mob turncoat William Marshall told the feds that around July or August 1997, Gigante’s nephew, Salvatore, asked Gambino soldier Craig DePalma to offer money to a marshal assigned to drive jurors.

Acting at the Oddfather’s behest, Sal Gigante asked DePalma to persuade a cousin, who was a marshal, to offer the cool million to the marshal guarding the jury.

“Gigante told DePalma he wanted to pay this U.S. marshal one million dollars to come forward and say that he had heard something from the jurors that would help his [Gigante’s] case,” the report stated.

DePalma told Marshall that he contacted his marshal cousin about two weeks after Gigante made the offer, the report stated.

“DePalma’s cousin responded that he [DePalma] should have contacted him earlier and that had he done so, then he [the cousin] might have been able to do something,” the report stated.

A probe into Marshall’s allegations has not resulted in charges.

“If in fact a marshal was approached with a million-dollar bribe, why wasn’t an arrest made?” said Gigante’s lawyer, Michael Marinaccio. “Why wasn’t an indictment brought?”

But alleged jury misconduct was part of Gigante’s effort to win a new trial.

In August 1997, Gigante’s lawyers learned jurors had discussed the case before deliberations from a prisoner, who was hospitalized under marshals’ custody and was being guarded by retired cop Alfred Santoro.

The defense hired a private eye, who sent “an attractive and flirtatious female” undercover to get Santoro to spill his guts about improper discussions jurors had while he chauffeured them. Santoro was caught on tape discussing jurors’ statements about the case and the Gigante family.

After a hearing in which Santoro was grilled, Judge Jack Weinstein decided in May 1999 not to query jurors and closed the matter.

“This just proves the Chin is out of his mind,” said lawyer Ron Kuby, whose client initially revealed Santoro’s claims to Gigante’s defense team. “There was all this real misconduct going on, and there was no need to spend hard-earned money to concoct any.”